Quantification of Water Content and Speciation in Synthetic Rhyolitic Glasses: Optimising the Analytical Method of Confocal Raman Spectrometry

Abstract

Quantification of water content in silicate glasses is of vital significance in understanding magma evolution and metamorphic anataxis. Here we provide a method for the determination of total dissolved water content and water speciation in silicate melts by confocal laser Raman spectrometry based on a set of hydrous rhyolitic glasses. A series of alumino‐silicate glasses with water contents from 0.33 to 9.05% m/m were synthesised in a piston cylinder apparatus. Synchrotron‐FTIR mapping shows that these glasses have relatively homogeneous distributions of dissolved water. Total water contents of the glasses were precisely measured by TC/EA‐MS and FTIR. Both external and internal calibration were established for the quantitative analysis of water content and water speciation in the silicate glasses based on excellent linear correlation between total dissolved water content and integrated area of the water Raman band. Furthermore, by decomposing the total water Raman bands into four Gaussians components, the relative concentration of water speciation (OH groups and molecules H2Om) dissolved in the glasses was determined with a similar trend to water speciation data derived from FTIR. We suggest that the relative concentration of water speciation can be estimated in rhyolitic glasses with 4–8% m/m H2O. Our work provides an accurate method to determine total water content and a potential tool to limit the relative concentration of water speciation dissolved in silicic glasses.

Quantification Of Water Content In Glass At Nanoscale Using Atom Probe Tomography

“…This may be due to the significant abundance of molecular H2O in addition to hydroxyl in both RH-4 and RH-9, as determined by previous studies. 12 However, if only the hydroxyl contents in RH-4 and RH-9 were used, a good linear correlation with an R 2 of 0.9306 for the calibration line was obtained. This bias likely results from the loss of most molecular water during FIB preparation or the ultra-high vacuum conditions of APT, while hydroxyl remains largely unaffected.…”

“…Five glass standards with trace amounts of water were selected for analysis, including Suprasil 3002 quartz glass, 22,[41][42][43] and rhyolitic glass chips OA-1, OH-1, 44 RH-4, and RH-9. 12 The total water content of the 3002, RH-4, and RH-9 glass standards were measured previously using FTIR, with determined hydroxyl contents of 9600 ± 200 μg/g for RH-4 and 16100 ± 100 μg/g for RH-9, as detailed in Table 1.…”

“…7,8 Traditional analytical techniques like Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) have been pivotal in characterizing water content and speciation in minerals and glass samples. [9][10][11][12][13][14] However, these methods are limited to samples larger than 10 microns, posing challenges for analyzing smaller or more complex structures, such as deep mantle analog samples synthesized by laser-heated diamond anvil cells (LH-DAC). 15 Recent advancements in secondary ion mass spectrometers (SIMS), including large geometry ion probes and NanoSIMS, have been used to analyze the water content in minerals like olivine, pyroxene, and feldspar, as well as in glass, achieving spatial resolution in the micrometer-to submicron range while maintaining excellent detection limits.…”

Atomic spectrometry update – a review of advances in environmental analysis

“…Quantification of the water content in silicate glasses is important in understanding magma evolution and metamorphic reactions. Tu et al 253 described a confocal Raman spectrometry method to measure the content and speciation of water in silicate melts. Synthetic rhyolitic glasses prepared with water contents of 0.33 to 9.05 wt% were shown by synchrotron-FTIR mapping to be relatively homogeneous.…”